I think there is also a concept called early z and late z. In case shader is looking up for a texture where it can modify the original z value (like displacement mapping?), then it could change how the final Z value. What we are looking is early z value. It is possible that in real rendering, late z is also enabled. We just update the Z buffer after shader is run. However, we would lose the benefits of hidden surface removal for correctness..
I think there is also a concept called early z and late z. In case shader is looking up for a texture where it can modify the original z value (like displacement mapping?), then it could change how the final Z value. What we are looking is early z value. It is possible that in real rendering, late z is also enabled. We just update the Z buffer after shader is run. However, we would lose the benefits of hidden surface removal for correctness..